Since you seem to know a little more about this BMS functionality, what do you have your overvoltage settings at? I have mine at 4.2 but I think that I triggered overvoltage and it stopped taking reverse current when I was braking near full battery
The problem is if you set it higher, when you’re charging it lets the top cell get to that voltage and then waits for it to go back down
These are my settings. I had lowered the over voltage from 4.25 when I was doing the initial balance on the pack and never bumped it back up. I generally keep it in balance charging mode since the pack is still under 50 full cycles and doesn’t have much trouble keeping balanced. But if its outside the threshold after charging ill switch to static balance. Also lowering the switch on voltage to 4V, or lower, is beneficial that way it will balance for a much longer time span.
Alright thanks that helps, I’ll compare to mine when I connect
Lets chat about these 2 cells…
So cell 1 is the one i blew last week… I’m getting into removing.it now to notice cell 2 which welded fine has a.similar discoloring or wetness under the wrapper…
Thoughts?
And naturally my multimeter is dead.for.some reason so.have to run out and get a new one here now…
1 and 2 both had charge…which i find interesting for 1 being a blown cell that let out magical juice… i replaced both since i was there anyways but would still love anyones feedback on #2 based on the weird under wrapper appearance… pack is done…waiting on bms and flux deck is basically ready for the road!
Okay, so my cells and BMS came. Now I’ve just got to wait for my spot welder to arrive before I start making my pack. Here’s my revised diagram:
I’ve been reading about how much nickel strip I actually need, and it seems like 1 layer (of 3 individual strips that are 0.2mm x 10mm) seems to be enough for the parallel connections (since the current is shared across all 4 cells), and 2 12AWG wires should be enough for the serial connections (where a lot of current will travel between battery groups). Is my understanding correct/are these amounts of nickel and wire safe for a 10s4p S30Q pack?
Check out @b264’s post on conductor current ratings. I think that’s pretty well thought out. Just make sure your soldering is on point for those series connections. Also, in your diagram, the nickel is only spotwelding between each cell and not across the entire P group. I hope that’s not actually how you’re gonna assemble it and that it’s just how you decided to draw it out 
And don’t forget the fishpaper in between!
This. Inside each P-group the cells can be separated only with their PVC jackets, but each P-group needs to have fishpaper between those cells and any other P-group.
I like how need is a link to the conductor current rating chart. 
so I won’t direct you there as well.
yeah what’s with the diagram?
when you say 3 strips and then draw them like the diagram do you intend to lay it out that way?
I’ve got my fishpaper too 
Sorry I’m braindead I’ve been digging through the forum all day; the three nickel strips on each battery group should be overlapping, my bad.
I looked at the thread earlier but apart from there not being any data for 0.2mm x 10mm nickel, I didn’t understand if the amount of current the nickel strips in total would triple in the potential of what it can handle if you welded 3 together (across each cell in a battery group)?
The closest sized nickel strip with the current spec on the chart is the 0.15mm x 10mm strips’ with an optimal operating current of 17a. My thought is that my 0.2 x 10mm strips can handle that much if not maybe more because of its extra thickness.
If one strip of 0.15mm x 10mm can handle 17a, does that mean 3 welded together can handle 51 amps? Or does that not make any sense (ya boy don’t get it )
Does it mean that once I weld across the 4 cells with 3 overlapping strips, it’s “comfortable” operating current is only 18.89a? And the only way I could increase the “comfortable” operating current of each battery group would be to layer extra strips of nickel (or some other conductor) over the first layer?
3 in parallell can handle 3x so yeah 51A.
but they have to be in parallell. not some form of overlapping series. which i’m still worried your diagram might imply.
yeah I didn’t think it through when making the diagram, I was planning on doing something like this:
Ok. that’s effectively in series. so you’re getting one layer’s worth.
usually people put a strip across the entire pgroup.
then if they need more current capacity they put another layer on.
then to avoid soldering on the cells they usually do some tabs off of that to come up to the series connections.
and I haven’t touched on your original question about how thick and why yet :).
right now I’m wishing there was a filter this thread for images mechanism so I could find you some good reference pics quickly.
Ahhh okay.
How does this look (as opposed to my misunderstanding earlier lol)?:
For how many layers to use?
Yeah that’s better. now you’ll find that 3 layers is uncommon and possibly not needed because the next magic trick. the current is split between your two upstream series connections. so if the path to them is even then your nickel for pgroup to series points only has to carry half the current. roughly.
really you just need to think about the paths from the cells to the series connections.
so if you’re targeting 4cell * 15A = 60A exiting via 2 evenly placed series connections then you need about 30A worth of nickel. but it could even be 15A worth of nickel off each cell to the series connection.
so I was trying to give you hints of how to think about it. i’m still only learned from reading myself.
I think you should find a picture of how one of the experienced battery builders in this thread do it for reference. then ask for confirmation on size of nickel for that layout. because layout would matter.
yeah by thick I meant in total… how many layers
This is the one huge 0.2mm piece of nickel approach people have been using for larger amp capacities.
note the series connections go on the folded over tabs.
I didn’t find the one I was thinking of where I think it’s @glyphiks does 8 or 10mm strip across the pgroups and then tabs off each cell in the pgroup in a triangle up to the series connections points folded over the top.
anyhow layout matters.
